Field
The present invention relates to a backlight unit, and more particularly, to a backlight unit capable of minimizing a non-light emitting region at an edge thereof while realizing a slim structure.
Discussion of the Background
General backlight units are broadly used for liquid crystal displays or surface lighting.
Backlight units of liquid crystal displays can be classified into direct type and edge type backlight units according to locations of light emitting devices.
The direct type backlight units have been mainly developed along with production of large-size liquid crystal displays having a size of 20 inches or more, and include a plurality of light sources under a diffusive plate to directly emit light towards a front side of a liquid crystal display pane. The direct type backlight units are mainly used in large-screen liquid crystal displays requiring high brightness due to higher light use efficiency than the edge type backlight units.
The edge type backlight units are mainly applied to relatively small liquid crystal displays such as monitors of laptop computers and desktop computers. Such an edge type backlight unit has good uniformity of light and long lifespan, and is advantageous in thickness reduction of a liquid crystal display.
FIG. 1 is a schematic sectional view of a backlight unit of a general small liquid crystal display device
Referring to FIG. 1, a backlight unit 100 of a general small liquid crystal display includes a housing 170, which is open at an upper side thereof and receives a reflective sheet 160, a light guide plate 150 and optical sheets 130 therein; a circuit board 111, and a light emitting device 110, which are disposed at one side of the housing 170.
The backlight unit 100 constitutes one module by attaching a light shielding tape 190 to an upper surface of the circuit board 111 and to a portion of an upper surface of the optical sheets 130.
Although not shown in detail, the light emitting device 110 includes a light emitting diode chip mounted inside a frame and has a package structure.
The light guide plate 150 includes a first area (FA), which has a gradually decreasing thickness with increasing distance from an area adjoining the light emitting device 110, and a second area (SA) having a constant thickness. Here, the general package type light emitting device 110 has a limit in realizing size reduction to a certain size or less due to structural features thereof. Thus, the first area (FA) has a light incident face corresponding to the size of the light emitting device 110, and has a gradually decreasing thickness corresponding to the thickness of the second area (SA).
The general backlight unit 100 can minimize loss of light emitted from the light emitting device 110 using the light guide plate 150 including the first area (FA) having a gradually decreasing thickness. However, the general backlight unit 100 has a limit in thickness reduction of the light guide plate 150 due to the size of the light emitting device 110. Thus, there is a difficulty following recent trend of decreasing the thickness of backlight units. Moreover, the first area (FA) has a slope 151 on an upper portion thereof thereby causing problems such as light loss due to light leakage, total reflection, and the like.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form any part of the prior art nor what the prior art may suggest to a person of ordinary skill in the art.